Method for manufacturing array substrate of transmissive liquid crystal display

ABSTRACT

A method for manufacturing an array substrate of a transmissive LCD includes: (1) providing a substrate; (2) forming a transparent electrode layer on the substrate and forming a first metal layer on the transparent electrode layer; (3) applying a first photo-masking operation to form a gate terminal and a pixel electrode; (4) forming an insulation layer on the gate terminal and the pixel electrode; (5) applying a second photo-masking operation to form a gate insulation layer on the insulation layer; (6) forming a semiconductor layer on the gate insulation layer and forming a second metal layer on the semiconductor layer; and (7) applying a third photo-masking operation to form a channel layer on the semiconductor layer and also forming a drain terminal and a source terminal on the second metal layer, so as to form a thin-film transistor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the technical field of liquiddisplaying, and in particular to a method for manufacturing an arraysubstrate of a transmissive liquid crystal display (LCD)

2. The Related Arts

Displays that are currently available in the market can be roughlydivided into three categories according to the light source used,including transmissive LCD, reflective LCD, and transflective LCD. Thetransmissive LCD is applicable in conditions of weak surrounding light,such as indoor environment. When used outdoors, due to the intenseexternal light, the intensity of the backlight source is severelyaffected, making human eyes perceiving excessive panel brightness andthus making image unclear, and eventually affecting image quality. Inaddition, long term use of the backlight source would lead to a greatconsumption of electrical power. Since a small-sized display is oftenpowered by electrical battery, it often occurs that power storage soongets exhausted. The reflective LCD is applicable for conditions withintense external light source for in the structure thereof, a reflectoris provided for reflecting away the intense light in order to minimizethe influence of the external light source. Such a structure is compactand light-weighted and saves power consumption. However, a problem ofinsufficient lighting may occurs in the conditions of weak surroundinglighting, and thus affecting the image quality. The transflective LCDhas two different display modes. In a dark environment, a transmissivemode dominates, where a backlight source of the LCD emits light througha liquid crystal panel to display image; and in a condition wheresufficient lighting exists, such as sunlight, a reflective modedominates, where a reflector of the liquid crystal panel reflects awaythe external light to serve as light source for displaying image. Thus,the transflective LCD is fit for various outdoor environments withintense lighting, and can particularly provide excellent outdoorviewability but requires only less brightness of the light source andshows an advantage of low power consumption.

An LCD is generally composed of an upper substrate and a lower substratebetween which liquid crystal is interposed. The upper substrate is theso-called color filter substrate, which generally comprises a commonelectrode and a color filter. The lower substrate is the so called arraysubstrate, which generally comprises thin-film transistor (TFT) andpixel electrode. The color filter substrate forms the color filterthrough multiple photo-masking operations. The array substrate usuallyuses four to six masks and is subjected to multiple masking processesincluding film deposition, mask exposure, and etching to form arrayedarrangements of thin-film transistors and pixel electrodes. The greaterthe number of mask used in the array substrate manufacturing process is,the greater the number of manufacturing steps has to be taken. Thisleads to high disqualification rate and makes it hard to control costs.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method formanufacturing an array substrate of a transmissive liquid crystaldisplay (LCD), which simplifies the manufacturing process of an arraysubstrate, shortens the manufacturing time, and reduces themanufacturing costs.

To achieve the above object, the present invention provides a method formanufacturing an array substrate of a transmissive LCD, which comprisesthe following steps:

Step 1: providing a substrate;

Step 2: forming a transparent electrode layer on the substrate andforming a first metal layer on the transparent electrode layer;

Step 3: applying a first photo-masking operation to form a gate terminaland a pixel electrode of a predetermined pattern, wherein the pixelelectrode is formed with the transparent electrode layer and is exposedand the gate terminal is formed with the transparent electrode layer andthe first metal layer;

Step 4: forming an insulation layer on the gate terminal and the pixelelectrode;

Step 5: applying a second photo-masking operation to form a gateinsulation layer of a predetermined pattern on the insulation layer;

Step 6: forming a semiconductor layer on the gate insulation layer andforming a second metal layer on the semiconductor layer; and

Step 7: applying a third photo-masking operation to form a channel layerof a predetermined pattern on the semiconductor layer and also forming adrain terminal and a source terminal of a predetermined pattern on thesecond metal layer, so as to form a thin-film transistor, wherein thedrain terminal is electrically connected to the pixel electrode.

The first photo-masking operation uses a grey-tone mask or a half-tonemask to perform exposure, development, and etching on the transparentelectrode layer and the first metal layer to form the gate terminal andthe pixel electrode of a predetermined pattern. The gate terminal isformed on the substrate with a portion of the transparent electrodelayer and a portion of the first metal layer that is disposed on saidportion of the transparent electrode layer. The pixel electrode and thegate terminal are spaced from each other. The pixel electrode is formedwith another portion of the transparent electrode layer.

The third photo-masking operation uses a grey-tone mask or a half-tonemask to perform exposure, development, and etching on the semiconductorlayer and the second metal layer to form the channel layer, the drainterminal, and the source terminal of a predetermined pattern. Thechannel layer is formed on the gate insulation layer and partly extendsto the pixel electrode. The drain terminal and the source terminal arespaced and respectively arranged at two ends of the channel layer. Thedrain terminal has an end extending along the channel layer to reach thepixel electrode.

The transparent electrode layer comprises indium tin oxide layer.

After Step 7, Step 8, in which a planarization layer is formed on thethin-film transistor, is included.

The planarization layer of Step 8 comprises a transparent insulationlayer.

The first metal layer, the second metal layer, and the transparentelectrode layer are formed with sputtering operations.

The insulation layer, the semiconductor layer, and the planarization areformed with chemical vapor deposition operations.

The efficacy of the preset invention is that the present inventionprovides a method for manufacturing an array substrate of a transmissiveLCD, which uses only three photo-masking operations to complete themanufacture of array substrate of transmissive LCD, thereby simplifyingthe manufacturing process, shortening the manufacturing time, andreducing the manufacturing costs.

For better understanding of the features and technical contents of thepresent invention, reference will be made to the following detaileddescription of the present invention and the attached drawings. However,the drawings are provided for the purposes of reference and illustrationand are not intended to impose undue limitations to the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical solution, as well as beneficial advantages, will beapparent from the following detailed description of an embodiment of thepresent invention, with reference to the attached drawings. In thedrawings:

FIG. 1 is a flow chart showing a method for manufacturing an arraysubstrate of a transmissive liquid crystal display (LCD) according tothe present invention;

FIGS. 2-6 are schematic views showing steps of the manufacture of anarray substrate of a transmissive LCD according to an embodiment of thepresent invention; and

FIG. 7 is a schematic view showing another structure of the arraysubstrate that is manufactured with the method for manufacturing anarray substrate of a transmissive LCD according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To further expound the technical solution adopted in the presentinvention and the advantages thereof, a detailed description is given toa preferred embodiment of the present invention and the attacheddrawings.

Referring to FIGS. 1-6, the present invention provides a method formanufacturing an array substrate of a transmissive LCD, which comprisesthe following steps:

Step 1: providing a substrate 100, wherein the substrate 100 is made ofa light-transmitting material and is generally a glass substrate, aquartz substrate, or a substrate of other suitable material.

Step 2: forming a transparent electrode layer 200 on the substrate 100and forming a first metal layer 300 on the transparent electrode layer200 (see FIG. 2), wherein the transparent electrode layer 200 comprisesan indium tin oxide (ITO) layer and the transparent electrode layer 200and the first metal layer 300 are made with sputtering operations, thematerial of the first metal layer 300 being molybdenum, tungsten,chromium, aluminum, copper, or laminations thereof, or other suitablematerial.

Step 3: applying a first photo-masking operation to form a gate terminal20 and a pixel electrode 30 of a predetermined pattern (see FIG. 3),wherein the pixel electrode 30 is formed with the transparent electrodelayer 200 and is exposed, and the gate terminal 20 is formed with thetransparent electrode layer 200 and the first metal layer 300.

The first photo-masking operation uses a grey-tone mask or a half-tonemask to perform exposure, development, and etching on the transparentelectrode layer 200 and the first metal layer 300 to form the gateterminal 20 and the pixel electrode 30 of the predetermined pattern. Thegate terminal 20 is formed on the substrate 100 with a portion of thetransparent electrode layer 200 and a portion of the first metal layer300 that is disposed on said portion of the transparent electrode layer200. The pixel electrode 30 and the gate terminal 20 are spaced fromeach other. The pixel electrode 30 is formed with another portion of thetransparent electrode layer 200. The first photo-masking operation iscarried out by coating a layer of photo-sensitive material, namely aphotoresist layer, on the first metal layer 300 and then projectinglight through the grey-tone mask or the half-tone mask to irradiate thephotoresist layer for exposure of the photoresist layer. Since thegrey-tone mask or the half-tone mask carries thereon a pattern of sourcezone, allowing a portion of the light to transmit through the grey-tonemask or the half-tone mask to irradiate the photoresist layer makes theexposure of the photoresist layer selective by which the pattern of thegrey-tone mask or the half-tone mask is completely duplicated on thephotoresist layer. Then, a proper developer is applied to remove aportion of the photoresist, making the photoresist layer show thedesired pattern. Then, an etching operation is applied to remove aportion of the first metal layer 300 and a portion of the transparentelectrode layer 200. The etching operation used herein can be wetetching, dry etching, or both. Finally, the remaining patternizedphotoresist layer is completely removed to form the gate terminal 20 andthe pixel electrode 30 of the predetermined pattern.

Step 4: forming an insulation layer 400 on the gate terminal 20 and thepixel electrode 30 (see FIG. 4), wherein the insulation layer 400 isformed through chemical vapor deposition (CVD) and the insulation layer400 is usually an oxide layer or can alternatively be a nitride layer,or a layer of a suitable insulation material, or a composite layer ofthese insulation layers.

Step 5: applying a second photo-masking operation to form a gateinsulation layer 40 of a predetermined pattern on the insulation layer400 (see FIG. 5).

Step 6: forming a semiconductor layer (not shown) on the gate insulationlayer 40 and forming a second metal layer (not shown) on thesemiconductor layer, wherein the semiconductor layer is formed with CVDand the semiconductor layer is a polysilicon layer; the second metallayer is formed with sputtering and the material of the second metallayer can be molybdenum, tungsten, chromium, aluminum, copper, orlaminations thereof, or other suitable material.

Step 7: applying a third photo-masking operation to form a channel layer50 of a predetermined pattern on the semiconductor layer and alsoforming a drain terminal 60 and a source terminal 70 of a predeterminedpattern on the second metal layer (see FIG. 6), so as to form athin-film transistor (TFT), wherein the drain terminal 60 iselectrically connected to the pixel electrode 30.

The third photo-masking operation uses grey-tone mask or half-tone maskto perform exposure, development, and etching on the semiconductor layerand the second metal layer to form the channel layer 50, the drainterminal 60, and the source terminal 70 of the predetermined pattern.The channel layer 50 is formed on the gate insulation layer 40 andpartly extends to the pixel electrode 30. The drain terminal 60 and thesource terminal 70 are spaced and respectively arranged at two ends ofthe channel layer 50. Further, the drain terminal 60 has an endextending along the channel layer 50 to reach the pixel electrode 30 toform the TFT. The third photo-masking operation is the same as theprevious photo-masking operations and it is noted here that in theetching operation, the portion of the channel layer 50 corresponding tothe drain terminal 60 is excessively and partly etched so that an endportion of the drain terminal 60 loses support and thus extends atop thepixel electrode 30 to allow the drain terminal 60 and the pixelelectrode 30 to be electrically connected.

Step 8: forming a planarization layer (not shown) on the TFT, whereinthe planarization layer comprises a transparent insulation layer formedthrough CVD.

Referring to FIG. 7, a schematic view is given to show another structureof array substrate that is manufactured with the method formanufacturing array substrate of transmissive LCD according to thepresent invention. The array substrate formed with such a structure isdifferent from the previous manufacturing process in that in Step 7, thethird photo-masking operation uses the grey-tone mask or the half-tonemask to carry out exposure, development, and etching on the insulationlayer so that the drain terminal 60′ formed on the semiconductor layeris completely located in the channel layer 50 and the drain terminal 60′is electrically connected through the channel layer 50 to the pixelelectrode 30.

In summary, the present invention provides a method for manufacturing anarray substrate of a transmissive LCD, which uses only threephoto-masking operations to complete the manufacture of an arraysubstrate of a transmissive LCD, thereby simplifying the manufacturingprocess, shortening the manufacturing time, and reducing themanufacturing costs.

Based on the description given above, those having ordinary skills ofthe art may easily contemplate various changes and modifications of thetechnical solution and technical ideas of the present invention and allthese changes and modifications are considered within the protectionscope of right for the present invention.

What is claimed is:
 1. A method for manufacturing an array substrate ofa transmissive LCD (Liquid Crystal Display), comprising the followingsteps: Step 1: providing a substrate; Step 2: forming a transparentelectrode layer on the substrate and forming a first metal layer on thetransparent electrode layer; Step 3: applying a first photo-maskingoperation to form a gate terminal and a pixel electrode of apredetermined pattern, wherein the pixel electrode is formed from thetransparent electrode layer and is exposed and the gate terminal isformed from the transparent electrode layer and the first metal layer;Step 4: forming an insulation layer on the gate terminal and the pixelelectrode; Step 5: applying a second photo-masking operation to form agate insulation layer of a predetermined pattern on the insulationlayer; Step 6: forming a semiconductor layer on the gate insulationlayer and forming a second metal layer on the semiconductor layer; andStep 7: applying a third photo-masking operation to form a channel layerof a predetermined pattern on the semiconductor layer and also forming adrain terminal and a source terminal of a predetermined pattern on thesecond metal layer, so as to form a thin-film transistor, wherein thedrain terminal is electrically connected to the pixel electrode.
 2. Themethod for manufacturing an array substrate of a transmissive LCD asclaimed in claim 1, wherein the first photo-masking operation uses agrey-tone mask or a half-tone mask to perform exposure, development, andetching on the transparent electrode layer and the first metal layer toform the gate terminal and the pixel electrode of the predeterminedpattern, the gate terminal being formed on the substrate from a portionof the transparent electrode layer and a portion of the first metallayer that is disposed on said portion of the transparent electrodelayer, the pixel electrode and the gate terminal being spaced from eachother, the pixel electrode being formed from another portion of thetransparent electrode layer.
 3. The method for manufacturing an arraysubstrate of a transmissive LCD as claimed in claim 1, wherein the thirdphoto-masking operation uses a grey-tone mask or a half-tone mask toperform exposure, development, and etching on the semiconductor layerand the second metal layer to form the channel layer, the drainterminal, and the source terminal of the predetermined pattern, thechannel layer being formed on the gate insulation layer and partlyextending to the pixel electrode, the drain terminal and the sourceterminal being spaced and respectively arranged at two ends of thechannel layer, the drain terminal having an end extending along thechannel layer to reach the pixel electrode.
 4. The method formanufacturing an array substrate of a transmissive LCD as claimed inclaim 1, wherein the transparent electrode layer comprises indium tinoxide layer.
 5. The method for manufacturing an array substrate of atransmissive LCD as claimed in claim 1, wherein after Step 7, Step 8, inwhich a planarization layer is formed on the thin-film transistor, isincluded.
 6. The method for manufacturing an array substrate of atransmissive LCD as claimed in claim 5, wherein the planarization layerof Step 8 comprises a transparent insulation layer.
 7. The method formanufacturing an array substrate of a transmissive LCD as claimed inclaim 1, wherein the first metal layer, the second metal layer, and thetransparent electrode layer are formed via sputtering operations.
 8. Themethod for manufacturing an array substrate of a transmissive LCD asclaimed in claim 5, wherein the insulation layer, the semiconductorlayer, and the planarization layer are formed with chemical vapordeposition operations.